The visitors dominated the first period before the Merseysiders rallied superbly later to be rewarded with a late equaliser.
Brighton made the early running without threatening and it needed a fine saving tackle by Tommy Elphick to deny Enoch Showunmi as Tranmere countered before Casper Ankergren saved well from Joss Labadie.
Brighton went ahead after 35 minutes with a fine 30-yard volley by Glenn Murray after a long clearance by Ankergren glanced off Ian Goodison. They should have at least doubled their lead before the break but Ashley Barnes blazed over from close range and misdirected a header.
There was a real scare for Brighton in the 53rd minute with an excellent left-foot shot by Showunmi from just outside the box striking a post. The striker saw another effort deflected agonisingly wide on the hour after good work by Dale Jennings before his cross after 62 minutes was turned onto the outside of the woodwork by Lewis Dunk.
Tranmere finally levelled when loan signing Scott Wootton headed home from an Aaron Cresswell free-kick in the 87th minute.